> We are still interested in contributing dynamic database API upstream.

Thank you.

> Please, can you provide more detailed requirements for contributing code?
> 
> I would like to get information about:
> - requirements to API tests

Minimally, we'd like a system-level test (such as the ones in
bind9/bin/tests/system).  Those tests generally run one or more
named servers listening on different loopback alias addresses,
and exercise features of them at runtime.  There are "dlz" and
"dlzexternal" tests you might have a look at to get an idea.

In the past few years we've also started introducing unit tests
written using the NetBSD "ATF" testing framework.  Those appear in
bind9/lib/isc/tests and bind9/lib/dns/tests.

> - requirements to documentation: Is enough to comment code in the same 
> way as BIND?

API comments with doxygen directives such as BIND uses would be helpful.
I would also suggest a README file for implementors, to be included
with the sample driver.